I like it, use a super fast, low noise opamp to do the summing and monitor the output.
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By chance did an amp with ungodly high TIM happen to be a Crown DC-300? [What an overrated POS]
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I worked part time in college at an odd specialty electronic shop that did all sorts of custom electronics, everything from stepping relay PBXs to exotic high end audio. We sold an early Haffler integrated ?100?W amp to a biker bar. It was only time in my life when a boss ordered me "Carry your pistol and be prepared to use it." There were 5 of us armed to the teeth.
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It was one of the most frightening jobs I was ever on.
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School got too busy the next semester (trying to carry two majors, EE and physical anthropology was somewhat demanding time wise.....] so I lost track of any follow up. [The bar was still there last June when we drove past.]
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I've often how long the amp lasted before it was stolen, blown up or had beer poured in it.?
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It felt [it was!] like a major sacrilege against everything good in the universe to put such a good amp in such a dive with the best JBL speakers of the time.
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That was the first and last biker bar we did and I still get the shakes.
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Now Johnny Angels was a very different bar...being 22 and naive I had no idea there were gay bars....
They wanted a very fancy disco system. I'd have had to design a light sequencer using a Motorola 6800. [I hated programming, still do.] We passed on that gig.
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Much much later, when I worked at the university we were taking a break from setting up a major production in Lexington's classiest hotel, went to the cafeteria and a very pretty young lady got way too close to me? with some really odd body language.
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A coworker cut her off, "Lady he can't afford you."
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That was the moment I realized she was a working girl.....
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I had to hotwire our work van when we were in Dayton because the supervisor lost the keys. Theory became practice. The van was pre steering wheel lock. My coworkers gave me the oddest look when I said, "Oh no big deal, let me get under the dash." 30 seconds later the engine was running and then I got the really odd looks.
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I always thought it funny when TV/Movies made hot wiring out to be quantum mechanics. I learned how in a junkyard owned by a great uncle at 8. I hotwired an old junker and drove it about 200 feet right into a 100 year old oak tree. My father only laughed. Mom wasn't all that amused and muttered something about her only son is going to end up in prison.? [Not yet]
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Hey you try to steer, work the gas peddle, brake and a clutch you can barely press with short legs and your older sister screaming "We are gonna die!" as loud as she could. Once I got moving I couldn't stop ... well not under control.
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The oddest parts of my work life weren't technical.
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Oh damn, just remembered this device....
Sound Impairment Monitor - The Answer?
And
The ESP SIM (Sound Impairment Monitor)
Though this one only monitors the long tailed pair...not sure how accurate it would? be.
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The first unit is based on the Baxandall Subtractive Test Set and appeared in a ?mid 1960s? Wireless world. I should have mine, built it in EE to prove a point. Probably need better opamps, LM301A aren't exactly state of the art.
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I'll try to locate the Wireless World where it appeared. might take a week or so.
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Sorry for the mixed fonts.
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Found my SIM" it! God it is primitive, I used that funny ?Dymo? embossed plastic ribbon label maker. They don't hold up well after 50 years. Now to rebuild it and make new labels! [and a new power supply, zeners don't cut it!]
[I saved each and every piece of test equipment I made in EE then later at various jobs.]?
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I did a quick search and found this paper by David Haffler, he's doing the test very different then I expected.4
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And here is a reprint of the Baxandall audio test scheme.?
This works, it will show the minute differences between units of the same model.
I'd loved to have had a PC based FFT system back then.
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I'm betting if we can find a way to measure the subtle non linearities in Hfe in the transistors, we'll find the problem, then he gets to figure out how to design to minimize those variables. I'll borrow a tektronix curve tracer Monday.
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Now, what to bill him....
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